In a previous article we have seen that the best way to satisfy the electric mobility needs is a combination of a widespread of low power (3,7 kW) charging poles, light electric cars equipped with battery no larger than 40 kWh, and distributed automated battery exchangers capable of replacing batteries in 59 seconds.  So, there is no need more for any demand curtailing and the grid costs remain very affordable.

We could go very further if we would share our travels with at least one other commuter, eliminating the traffic jams and cutting commuting energy consumption by 50%.

As announced, this article treats of the second major topic about the myth of flexibility: dwelling heating.

There is no day where the expression heat pump is not touted as the ultimate solution to eliminate the CO2 emissions of our damned gas (central heating) boiler.  Another myth.

Let’s examine the key figures.  The average annual heating requirement for a dwelling is 15.000 kWh (15 MWh), while the average domestic electrical consumption (excluding heating and electric car charging) is about 2.500 kWh (2,5 MWh). This means heating needs are 6 times as high as all other electrical needs combined.

It’s important to note that this heating requirement is independent of the technology used to generate the heat. It’s simply the energy needed to maintain a comfortable indoor temperature (around 20°C) throughout the year, particularly during the winter months (October to April in Belgium). The actual energy consumption, in turn, depends on the technology used to produce this heat.

For a condensing gas boiler, the energy consumed is nearly equal to the heating needs. Heat pumps are often rated with a COP of 4 (thus produce 4 kWh of heat per 1 kWh of electricity consumed). However, with air-to-air (or air-to-water) heat pumps, this efficiency is only achievable when the outside temperature is above 10-15°C, thus when the heating needs are very low.  The actual effective COP of a heat pump is this much lower.

Other types of heat pumps exist with higher COP’s at lower outside temperatures, but they require floor heating, which isn’t feasible for existing dwellings. Only new dwellings with high investment budgets can be equipped with such systems.

Therefore, we will only consider affordable and achievable installations of heat pump, i.e. air-air and air-hot water ones.  This type of heat pump is very sensitive to the outside air temperature (for detailed info, see article: https://edenergy.be/heat-pumps-paradigm-or-fallacy/?lang=en).  To simplify estimations, let’s assume a COP of 4 during summer (June–August), 2 during mid-season (April-May and September-October), and 1,5 for winter (November-March).

Now, let’s consider how heating needs are distributed throughout the year. These needs are proportional to the temperature difference between inside and outside.  For an indoor temperature of 20°C, if the outside temperature is -10°C, the difference is 30°C; at 0°C, the difference is 20°C; and at 20°C, the difference is 0°C.

According to experts, heating needs become negligible when the outside temperature reaches 16°C. They use curves to convert outside temperature (plus wind, sun and weather conditions) into heating needs. These curves also include domestic hot water needs, which are much lower than heating needs and can thus be included without affecting overall results.

Using these curves, we find that the summer months account for 6% of annual heating consumption, mid-season months 21%, and winter months 73%. The 3 coldest months (December-February) alone account for 50% of the yearly needs, meaning 7.500 kWh are concentrated in these months, a huge amount compared to the 2.500 kWh annual electricity use for non-heating purpose. The distribution of the of these yearly 2.500 kWh, using the curves draw by experts, is rather of 33% over December-February, thus 833 kWh.

During these 3 months, if heating needs of 7.500 kWh are met by an air-to-air (or air-to-water) heat pump, with a COP of 1,5 (according to low outside temperature), the required electricity consumption for heating would be 5.000 kWh. This is 6 times as much as the electricity consumption for non-heating purposes over the same period.

Given that heat pump systems of this type have nearly null heating storage capability (a vessel of 700 litres does not enable more than 7-8% energy demand reduction; for the details, see article: https://edenergy.be/heat-storage/?lang=en), we can’t rely on a buffer to provide heating even for several hours, the consumption is directly driven by the instant need.

This means that widespread use of heat pump would (will ?) require a 6-fold increase in grid capacity, since we will never be able to catch/cover/delay/shift this huge need with flexibility.  Such grid capacity multiplication represents a monstrously huge investment, that will (of course) be charged on the grid users (each of us, and much more by residentials than by industrials).

If we consider that today grid costs have are split 50/50 between investment and operational costs, a 6-fold increase in grid capacity rises the total grid cost from 100% to 350%.  Yes, that is a multiplication by 3,5.  Without taking into account any increase in the operational costs, which will of course also be higher.

This figure means, for an average residential user, a grid costs increase from 300€/year to 1.050€/year.  At the same time, energy costs would rise from 525€/year for gas to 930€/year for electricity (with a usage-weighted average yearly COP of 1,61 for the heat pump: 15.000 / 1,61 = 9.300 kWh × 0,1 €/kWh). Taxes would also increase from 75€/year to 450€/year (electricity taxes are much higher than gas ones). While gas grid costs would be eliminated, they are only about 75€/year.

Thus, switching from a condensing natural gas boiler to an air-to-air (or air-to-water) heat pump would increase the annual heating bill from 675€/year to 2.430€/year, a 3,6-fold.

Moreover, the high electricity demand in December-February would likely drive prices even higher, and this demand cannot be managed through flexibility.

Consequently, the investment in renewable energy production would also need to increase 6-fold, without considering the necessary excess capacity to cover periods of low renewable source availability and high demand.

Criticism is necessary to put the reality in front of the deciders, but completing it with suggestions would, in my eyes, be much better.

A simple solution is to invest in thermal insulation for dwellings, supported by substantial subsidies (60-80% of costs with well-defined caps to prevent misuse). This could reduce heating needs by a factor 2 to 3, dramatically lowering energy demand. While the required investment would still be large, it would be much lower (factor 2 instead of factor 6).

Additionally, combining thermal insulation with hybrid (gas-fired) boilers (0,3-0,7 kW electric and 1,5 kW thermal CHP + 5 kW extra boiler + 2-5 kWh electric battery) would provide local (at dwelling level) heat and electricity production (without any transport loss), reducing the need for large-scale electricity production and grid capacity investments.

CO2 neutrality could be achieved by producing renewable methane from excess renewable electricity and captured CO2 from the hybrid boiler.

This approach will guaranty the continuous availability of heating at a very affordable cost for the individuals as well as for the society.